Transmitter having impulse modulation



Sept. 5, 1944. RME-GRAY 2,357,398

y TRANSMITTER HAVING IMPULSE MODULATION y Filednec. 19. 1941 FIG.

Patented Sept. 5, 1944 Richard Edmund'Gray, London, England, assignor toInternational StandardY Electric Corporation, New- York, N. Y

Application Deceinhenll), 1941, ServialN-o. 423,634 In France April 1,1940 (Cl. Z50-17.)

Claims.

y The present invention relates to impulse modulated transmitters whichareparticularly applicable to telegraph systems that use impulsemodulation.

The main object of the invention is the providing of transmitters forimpulse modulation systems that are sturdy, that occupy little space andthat do not comprise thermion'ic tubes.- Such transmitters are speciallysuitable for use asportable senders of telegraphic signals.

An impulse modulated telegraph sender that incorporatescharacteristicfeatures of the invention is disposedso as to emit starting andterminating impulses of signalsthat consist of wave trains produced inan oscillatory' circuit associated with the radiating antenna,th'e'impulses' being generated by a manipulation eifected'on theoscillatory-circuit. f

According to another characteristic featureof the-invention, themanipulation may be manual an'dmay be applied to the oscillatorycircuit, either manually or by meansl ofy a'- relay! located in avacuum. ,v l

According to another feature of the invention, means are provided forchangin'g'the',Wavelength of the 'starting and terminating impulsesiii-such a way as to insure'greater4 independence of the interferencesin the radio connection, and' a greater secrecy of the signals atv thesame time'.v In yone example of an embodiment, a tubeles's transmittingdevice for an impulse modulated telegraph system comprises a two-waykeywhich, in one position, controls the connectionof a condenser in anemitting antenna oscillatory circuit (comprising an inductance andA thiscondenser) and another condenser of the same value in aghigh frequencycharging circuit, the connections of the two condensers being reversedin theother position of the Ykey. The'discharges of the condensers sendthe brief starting and terminating impulses of each signal intovtheantenna and, if desired, the relative capacities of the condensers maybe regulated in order to insure afdnite change of frequency between thesaid starting and terminating impulses; r y

The invention will be explained in rdetailin the following descriptionof examples ofemb'd'i'fnent vantageously in the circuit'sof' the`transmitters of' Figs. 1 and2.

a way thatisexplained'further on; An antenna 'lois directly branchedv atsuitable points of the inductance 4; A source of high voltage 8 is'rconnected between contact 3 of key l and an intermediate point ofthe'connection that'permanently couples inductance 4 to the' twocondensers 5 and 6i The vmode of'operation caribe explained as follows:In'oneof its positions,A key'l connects one orA other of condensers 5and 6" to the indl'ictance 4v andconnects the other-condenser to thehigh'voltage source-l.` In the position shown in the drawing, forAexample, rkey I connects at its'contact 2 Vthe condenser 5 in closedcircuit with the inductance 4,;wl'i`1e atits contact 3 it connectscondenser Iitol theAv terminals of the high voltage source V8;A In thisway, conderisery S-is charged almost instantaneously over" the sourcetlg-while condenseris' discharged over inductance 4iV In theotherposition of the key,- tliefcorinections of vcondensers 5 and 6 Iarereversed, and it is condenser 5 that is charged bythe source 8, whilecondenser ll is discharged into inductance 4. Inductance l and condenser5" or 6j that "is vr`connected'tof it constitute a high frequency'circuit that is'L tuned tothe desired' frequencyor trailsmission. Theoscillatory dischargeY of the condenser over the'vin'ductance sendsout a'liiglfi frequency energy impulsev which is radiated vby the antenna'yT. I Y 1 It can thus be seen that annimpulse is sent withr` each changeofv position-.of key"` so that manipulation of the key upward anddownward, or'viceA versa depending onthe' normal position, causes thesending 4of a pair of impulses'spaced in time and of the durationrequired'fo'r marking afdot or a dash.A These impulses consequentlydefine'V the beginning and termination 0fl each telegraphic signal. A I

Thevr emitted signalscan berce'ived' with l'any receiver adapted 'toreceive y impulsefmodulated signals.v Receivers of this kind are wellknown per se andV do not call Vfor 'ayparticular description. Y

It is evident that if it is desiredto maintain a certain amountofsecrecy, or` only to 'increase the independencey withY respect* to 'theinterferences that vclar'acteri'z'e impulse modulation? sys- 'p 'pa-'irlmaybe" tr" "I mitteczlona diirereittfrequencyby select gun- 'egualjvalues'jfo' condensers 5`fand 6r iin affp're'determined ratio; .Y f fFig.' 2 illustrates" a modification offthelcircuit of *'Fig. '1 in v irhi`cl"1` key lt isfreplacedjbya two contact relay l U,- the operationVpf' whiclrfeff'ec'zts the relay is placed in an extreme vacuum, such asan electron discharge tube vacuum in order to avoid sparks and itscontacts when it is operating. It is controlled, as shown, by a simplemanual key II that is inserted in its exciter circuit. The' installationof relays of this kind in a vacuum...V

is known per se and is consequently not describedv j in detail.

The high voltage source 8 of Figs. 1 and 2 may'v be of any suitablekind. However, in order to have the entire apparatus retain theadvantages ling source, said condensers and said inductance that inea-ch position assumed by said signalling A means, one pre-chargedcondenser is connected directly to at least a portion of said inductanceto Y form an oscillatory circuit, whereby the respective reactances ofsaid condenser and said portion of said inductance determine theperiodicity of the of simplicity it enjoys from the above described- Aarrangements, it is preferable to provide this source as a high voltagevibratory system fed by a low voltage battery. Figs. 3 and 4 show twoexamples of known circuits of this kind of high voltage feeding systems,and these can be used directly in transmitters such as those describedabove, the terminal I2 of each of these circuits being connected tocontact 3 of key I or relay I0, and the terminal I3 of these circuits tothe point of permanent connection of source 8 to the oscillatorycircuit.

In the circuit of Fig. 3, a low voltage battery I 4, e. g. of 6 volts,has its direct current transformed into alternating current by thevibrating contact I5, and this alternating currenty has its voltageincreased by the transformer I6 whereupon it is rectified by the diodewhich recties the two alternations I1 and which has its plates connectedto the two ends o f the secondary of transformer I6. The rectified highvoltage current is transmitted through a filter I8 to the terminals I2and I3 to which 'the circuit of the described transmitter is connected.n

The equal resistances IS-IS' and the condenser are provided for thepurpose of preventing sparks at the vibrating contact I5, while the`condenser CI v is provided for absorbing transient currents that mightcause interferences in the output current.

The circuit of Fig. 4 illustrates a simpler form of thepvibratory highvoltage source. The current of battery 2l is transmitted to a vibratingarmaf ture 22 which is provided with two pairs of contacts that arerespectively connected to the ends of the primary and secondary windingsof the stepfup transformer 23, so that the direct current of battery 2I, after having been transformed into alternating current and raised involtage, is immediately rectied inthe secondary of the transformer.After filtering in 24, this high voltage rectified current is applied tothe terminals I2 yand I3 and consequently to the oscillatory circuit ofFigs. 1 and 2.

Although the invention has been described for the particular case ofcertain examples of embodiment, it is evident that itis by no meanslimited to the same, particularly as regards the actual form of thecontrol key of the oscillatory circuit and the high voltage feed of thiscircuit. It is, on the contrary, capable of numerous modiiications andadaptations without departing from its scope.

What is claimed is:

1. Radio transmitter for producing signals defined by. the lapse of timeextending from the transmission cfa first single train of damped osancehaving a predetermined reactance, means for producing in said inductanceboth said rtrains nfirst train of damped oscillations resulting fromsaid connection, and at the same time the recillations to thetransmission of a second single train of damped oscillations, includingan inductf maining condensers are connected to said charging source,said signalling means being likewise connectedso that the assumptionv ofanotherv position thereby will cause the connection to said inductanceof a second pre-charged condenser, so as to produce in the oscillatorycircuit formed .thereby a second train of damped oscillations, of aperiodicity likewise predetermined by the respective reactances of saidsecond condenser and said portion of said inductance to which it isconnected, the time elap'sing between successive positions of saidsignalling means being under manual control and being variable inextent, whereby a predetermined signal may be transmitted.

. 2,.,Animpulse modulated transmitter according to claim 1, wherein saidsignalling means comprises a vacuum relay and also including a manuallyoperable signal key so connected as to control the actuating circuit ofsaid vacuum relay.

3. An impulse modulated transmitter according to. claim 1, wherein saidfirst and second condensers yare of different capacities, whereby therespective shockV excited damped periodic oscillations constituting thestarting and terminating impulses, respectively, of a signal are ofdifferent frequencies.

r,4. An impulse modulated transmitter in which the signal elements aredefined in duration by starting and terminating impulses, comprising aninductance, first and second condensers, a charging voltage source forsaid condensers, a connection from one end of said inductance to onearmature of each of said condensers, a connection from one terminal ofsaid voltage source to both said last mentioned condenser armatures, anda two position switching device which in one position connects the otherend of said inductance to the other armature of said rst condenser andconnects the other terminal of said voltage source to the other armatureof said second condenser and which in the other positionrconnects thesaid other end of said inductance to said other armature of said secondcondenser and connects the said other terminal o f said voltage sourceto the said other armature of said first condenser, and whereby said rstcondenser connected to said charging source acquiresa static charge andupon connection to said inductance, discharges therethrough so as toproducea first train of damped waves constituting said starting impulseand having a periodicity predetermined by the electrical constants lofsaid condenser and said inductance, the connection of said secondcondenser in like fashonstosaid inductance producing a second similarlydetermined train of waves constituting Vsaid'terminating'impulse, thetime consumed in moving said switching device from one position to theother being under manual control so as to Q'dene a signal by temporal'characteristics, said transmitter also including means for transferringsaid respective trains of damped waves from said transmission purposes,and connection means bel0 tween said key and said inductance forconnecting, in each key position, a single pre-charged condenser inshunt to at least a portion of said inductance so as to form anoscillatory circuit of a frequency determined by the reactance of theelements thereof, whereby a damped pulse of oscillatory energy occurswhen said key makes contact at each position thereof.

RICHARD E. GRAY.

